The isolation of myelin and myelin subfractions during development and characterization of their protein and sphingolipid (cerebroside, sulfatide, ceramide and gangliosde) composition will be examined in control mice and in several murine mutants with disordered formation of maintenance of myelin: Jimpy, Quaking, myelin synthesis deficiency, wabbler lethal and dilute lethal. Comparisons will be made to other subcellular fractions and to membrane phospholipids. Myelin isolation will include the technique of cesium chloride density gradient centrifugation and of isolation of the 'myelin-like' fraction of Agrawal et al. (1970). Myelin proteins will be characterized by electrophoresis on polyacrylamide gel containing SDS or urea, and by peptide separation by two-dimensional chromatography and electrophoresis ("finger- printing") after in vivo isotopic labelling. Cerebrosides, sulfatides and ceramides are isolated by Florisil column chromatography and TLC and their molecular composition assayed by GC. Gangliosides are extracted by the method of Suzuki, resolved in an ascending TLC system and assayed for fatty acid, sphingosine and NANA content. The data concerning the composition of these major myelin constituents in several mutants should further understanding of the process of myelination particularly if identification of critical myelin components and deduction of their role in the formation of this membrane is suggested.